[Changes in the enterocyte population kinetics during the process of development of intestinal tumors in rats].

Changes in proliferation of the enterocytes from the descendent colon at different developmental stages of tumours induced with 1,2-dimethylhydrazine (DMH) were studied. As a result of carcinogen-induced disturbances in enetrocyte differentiation, the proliferative crypt zone was seen broadening, the proliferative cells appearing even in the mouths of the crypts. Further, these very superficial parts of the crypts proved to be the sites of carcinoma development in situ. During the tumour induction, the majority of enterocytes display short mitotic cycles which are somewhat longer than in the normal colon. The DMH treatment, even at early stages of the experiment, leads to the appearance of a high occurrence (up to 50--60%) of abnormal mitoses in enterocytes.